Supplementary Figure 1: CYRI proteins are evolutionarily conserved and contain a putative Rac1-binding site similar to CYFIP.

a - Co-evolution of Arp2/3 (green), Scar/WAVE (brown) and CYRI (orange) across the 4 main superfamilies of the eukaryotic tree 1. An incomplete circle corresponds to the absence of some subunits from the complex as in 2. Each supergroup was assigned to a specific background colour: Unikonts (yellow), Chromalveolates (pink), Excavates (blue) and Plants (green). Branch length does not reflect evolutionary distances. For C. elegans and R. allomycis, * and red highlight around circle denotes lack of putative N-terminal myristoylation site on CYRI (see below). Different coloured branches in Unikonts represent amoebazoa (yellow branches), metazoan (purple branches), fungi (brown branches) and Rozella allomycis, the earliest diverged of the fungi (blue branch). b - Alignment of D. discoideum and H. sapiens CYFIP and CYRI sequences. UniProt accession numbers are reported. Colour code represents the number of entries with identical amino acid at this position. c - HMM logo from the highlighted region in (b). Logo was generated by feeding the full Pfam dataset (915 sequences) of the DUF1394 domain to Skylign. Letter stack represents the conservation of the residue at this position across the dataset. Occupancy score is also mentioned below each letter (light blue) and is a readout of the presence of a letter across the dataset, ranging from 0 (no present) to 1 (present).